It's not every day that one of the most famous chefs and restauranteurs in the world shows up at your front door and offers to cook you lunch. But Ruth Rogers has a new cookbook out celebrating three decades since she co-founded London's iconic River Cafe. There are some new recipes in here, but it's mostly classics - the simple Italian cooking that has won the River Cafe so many foodie fans. The one she's offered to teach me is totally basic - only five ingredients.

RUTH ROGERS: It has bread. It has tomatoes. It has basil and a bit of garlic and the oil. And that's really it.

ROGERS: It's called Pappa al Pomodoro apparently because it's almost considered like Pappa - baby food. You know, this is something you would give a child.

(SOUNDBITE OF FOOD SIZZLING)

KELLY: Leave it to the Italians to make even baby food taste absolutely gorgeous. Rogers's husband's family is Italian, and she used to go visit them on the Tuscan coast every summer. One day, she told me she was reading up in her room when she overheard a massive fight erupt in the kitchen - two sisters making a pot of Pappa al Pomodoro and shrieking over whether to add a cup of water or just leave the tomatoes alone.

ROGERS: They were really arguing about, you know, what to do, what to do. And then it was really funny because the sister who only wanted the tomatoes won. But then I saw her - the other sister come back later and just pour a bit of water in.

(LAUGHTER)

ROGERS: I would say that Italian cooking varies from village to village, city to city, family to family and even sister to sister.

KELLY: Yeah. So for the record, Ruth Rogers dumped a big old cup of water in the Pappa al Pomodoro. Simmered and stirred. And that was it.

So how long should we let it cool while we talk here?

While the soup cooled, we pulled up chairs at my kitchen table to chat.

From the get-go - correct me if I'm wrong - you insisted on having a kitchen that was 50 percent women. Has it been hard?

ROGERS: I think it's - you know, it was started by two women. How do you make a better place of work? How do you make a place where being a chef, being a manager, being a waiter, being a pot washer or being whatever you are - that you come to work, and you want to come to work - so how do you do that? You have a mixed environment. Whether, you know, it's women in the kitchen, diversity in the restaurant is crucial. And I don't think women cook in a different way. I'd like to say that I couldn't tell if a risotto was made by a woman or a man or if I cook it. People sometimes say that, you know, oh, don't you love the way women cook? No, I think I like the way that people cook.

KELLY: Ruth Rogers loves to cook herself, as you've probably gathered. But you don't survive three decades in London, one of the most competitive restaurant cities in the world, unless you have a nose for business too. She says last year Harvard Business School sent two students to study the River Cafe and to make recommendations for how it might continue to thrive for another 30 years. They came up with four pitches.

ROGERS: One is that we open another restaurant just like it. The second one is that we do a kind of - which we often talked about - which is doing a kind of River Cafe cafe. So we'd have the cheaper things on the menu. You'd take the simpler things. And the third one was to do a product like our olive oil or to do ice cream. And what do you think the fourth one was? Do nothing.

KELLY: Do nothing?

ROGERS: Yeah. Stay as you are.

KELLY: And which did Rogers choose? That would be option four - the old if it ain't broke, don't fix it.

ROGERS: Look. It's growing. You know, we're doing better this year than last year. So I think we're good.

KELLY: Good because of Roger's focus on simple delicious food - food that I could not wait to taste. So we try it. We find bowls and spoons, a big ladle.

ROGERS: It's quite nice in a shallow bowl. You like it?

KELLY: I suppose this is the obvious thing. But when you just have a tiny handful of ingredients, you really taste them. I'm really tasting basil. I'm really tasting tomato. I'm really tasting garlic. And that's it.

ROGERS: And that's it.

KELLY: Ruth Rogers, her new cookbook is "River Cafe London: Thirty Years Of Recipes And The Story Of A Much-Loved Restaurant." Transcript provided by NPR, Copyright NPR.